Production of butadiene from 1, 3-butylene glycol



M. MUELLER-CUNRADI El AL 2, 5

PRODUCTION OF BUTADIENE FROM 1,3-BUTYLENE GLYCOL Filed July 20, 1937 Martin Mueder-6unrad Heinz .Kreked er INVENTORS THEIR ATTORNEYS Patented Dec. 19, 1939 BUTYLENE GLYCOL Martin MueIIer-Ounradi. Ludwigshaten-on-the- Rhine, and Heinz Krekeler, Mannheim, Germany, assignors to I. G. Farbenindustrie Aktiengesellschait, Frankiort-on-the-Main, Germany Application July 20, 1937, Serial No. 154,630 In Germany July 24, 1936 2 Claims. (01. act-cs1) The present invention relates to an improved process 01' producing butadiene from 1,3-butylene glycol.

It is already known that hydrocarbons having two conjugated double linkages can be prepared by heating. 1,3-glycols with agents splitting oil water in such manner that the hydrocarbons are removed from the reaction mixture as rapidly as possible. The process does not give satisfactory yields, however, in the preparation of butadiene from butylene glycol.

We have now found that butadiene can be obtained from butylene glycol by heating in the presence of agents splitting ofi water in the liquid phase, the yields being very good, by distilling oil! the reaction products formed, separating therefrom the intermediate products of the splitting 01! of water and returning them to the reaction chamber in such manner that at least a substantial proportion thereof enters into fractionating exchange. with the reaction products distilling ofi. v

The reaction is preferably carried out as follows:

A mixture of 1,3-butylene glycol and an agent promoting the splitting on oi. water is heated in a distillation still provided. with a fractionating apparatus. The mixture of water, butadiene and intermediate productsv of the splitting oil of water distilling oil are cooled to room temperature after leaving the fractionating apparatus.

There are thus formed two liquid phases, while the butadiene remains gaseous and is recovered separately. The upper layer ofthe liquid phases, consisting mainlyof a mixture of different intermediate products of the plitting oflf of water, is separated and returned holly or in a substantial proportion to the fractionating apparatus at the top. This return may be eifected continuously or discontinuously If returning only a substantial proportion, for example a third or the half of the intermediate products to the apparatus the residual proportion may be introduced into the apparatus in the usual manner, i. e. it may beintroduced directly into the liquid reaction mixture.

By the said measures. the temperature in the stillcan be kept at a value sufllcient for carry-" ing out the splitting on of water. Furthermore the removal of a part of the agents splitting oil water by distillation of the reaction mixture is prevented. Moreover further water is split off from the returned intermediate products so that 3 these are likewise converted into butadiene,

, are considerably reduced. The sulphonic acids whereby a considerable increase in the yield of butadiene is obtained.

Further butylene glycol, which has advantageously been preheated to the reaction temperature or higher, is supplied periodically or 5 continuously to the reaction mixture in amounts. corresponding to the amounts distilled oif. The amount of butylene glycol capable of conversion in the said manner in a single batch is only limited by the gradual enrichment in the distillation still of by-products incapable of being distilled oil at the reaction temperature. After interrupting the supply of butylene glycol, he contents of the still are further heated le gradually increasing the temperature as long as u butadiene is still formed. The residue, which is still sufflciently mobile at about 100 C.-, is then run oil from the still.

Itis important that-a mixture of butylene glycol and agent splitting off water should be present already at the beginning of the splitting ofi of water. For example, if the butylene glycol be allowed to flow onto the already heated agent ,for splitting 01f water, roaming and marked resinification take place From the lower layer oi the distillate, which mainly consists of water but which, still contains certain amounts of the said intermediate products, the latter may be recovered by fractional distillation and then also returned to'the first fractionating apparatus.

As agents splitting oii water there may be mentioned in particular organic sulphonic'acids. If these contain free mineral acids, the yields should therefore befree'from mineral acids, or the mineral acids contained therein must be neutralized, preferably bythe addition of an organic base, as for example aniline. An apparatus suitable for carrying out our process is diagrammatically shown in the accompanying drawing. In the drawing B represents the still. Before beginning the dehydration, butylene glycol together with the agent splitting oil water, are introduced through the pipe i. During the reaction fresh butylene glycol is-introduced in the same manner. 'Whe'n'the production of butadiene has ceased, the residue formed is .drawn oil through the stop cock 2. 0 represents -a fractionating column which is provided with filling bodies or bell-shaped condensing surfaces. (These are indicated in the drawing by means of the diagonal lines.) At the upper end of the fractionating column the vapors are drawn ofi through the pipe 3 and entered at 4 into the 55 cooling device -'K whioh is cooled by means of water atnormal temperatures. The uncondensed butadiene leaves the cooling device in gaseous form through the pipe 5. The condensate rormed in the cooling device flows therefrom through the pipe 6 into a separating vessel 1" in which two liquid phases are formed. The upper liquid layer is removed from the separating vessel through the pipe I and is introduced into the fflctionating column (3 at 8. The lower liquid layer which consists for the most part of water is drawn oil from the separating vessel 1" through the pipe 1. A .part oi the upper liquid from the separating vessel F may be introduced directly to the still 3 through the pipe Ill. The proportion of said upper liquid thus introduced to the still may be regulated by suitable adjustment of valves (indicated by crosses) in pipes l and Ill. The following example will turther illustrate how our present invention may be carried out in practice, but the invention is not restricted to this example. The parts are by weiaht.

Example 800 parts of 1,3-butylene glycol, parts or crude naphthalene sulphonic acid containing about 58 per cent of sulphonic acid, 7 per cent of tree sulphuric acid and 35 per cent of water, and 15 parts 01' aniline are heated to boiling in a still provided with a iractionatlng apparatus. From the beginning of the distillation onwards, further 1500 parts of 1,3-butylene glycol are gradually added. The substances distilled oil are condensed in the manner already described, the intermediate products 0! the splitting oi! of water separated and returned to the iractionating apparatus.

About 840 parts of very high percentage butadiene are thus obtained in all. Y

The temperature in the still amounts to from about to C. at the commencement of the splitting of! of water, is kept at from about to C. during the supply of the 1,3-

butylene glycol and is then gradually raised to tion. of 1,3-butyleneghrcol the stepswhich-comfrom 220' to 240' C. 1 I

when using purified toluene sulphonic acid instead of the naphthalene sulphonic acid, the

addition of aniline is unnecessary. The yield 0! 5 butadiene is the same. Benzene sulphonic acid may be used as the agent splitting oil waterin the same way.

What we claim is:

1. In the production of butadiene by dehydrationor 1,3-.-butylene glycol the steps which comprise heating. 1,3-butylene glycol in a still in the liquid phase in the presence of sulphonic acids of aromatic hydrocarbons, distilling oi! the reaction products formed consisting of butadiene,

water and the intermediate products of the dehydration of 1,3-butylene glycol, cooling the distillate to separate the butadiene from the water and said intermediate products, separating the intermediate products from the water and returning them to the still in such manner that they enter into i'ractionating exchange with the reaction products distilling oil.

2. In the production of butadiene by dehydraprise heating 1,3-butylene glycol in a still in the liquid phase in the presence of sulphonlc acids of aromatic hydrocarbons, distilling oil the reaction products formed consisting of butadiene, water and the intermediate products 0! the dehydration of 1,3-butylene glycol, cooling the distillate to separate the butadiene from the water and said intermediate products, separating the intermediate products from the water and returning at least a substantial proportion oi the intermediate products to the still in such a manner that they enter into iractionating exchange with the reaction products distilled oil,

the residual proportion being introduced directly into the still.

MARTIN MUELLER-CUNRADI. I-IEINZ KREKELER. 

